This invention relates to a chair that is used to support rebar and wire mesh during a concrete pour, and more particularly to a chair that is capable of supporting rebar and wire mesh in a wide range of sizes and at two different elevations.
In the pouring of concrete, metal reinforcements such as rebar or wire mesh are used to increase the strength of concrete. By itself, concrete is very strong in compression but surprisingly weak in tension. The inclusion of metal reinforcements in concrete increases the tensile strength substantially, allowing concrete to be used in many applications.
To increase strength, the metal reinforcements should be in the middle of the concrete, rather than toward one side. In a normal situation where a horizontal slab is being poured, this means the metal reinforcements should be above ground level and at about the center of the finished slab. It is accordingly necessary to provide a support, known as a chair, for the metal reinforcement to keep it off the underlying surface. Early on, the support was a rock or piece of brick. Chairs have evolved over time and become much more sophisticated.
There are a variety of chairs which have the capability of supporting different sized rebar. It is this type chair that this invention most nearly relates. Disclosures of interest relative to this invention are found in U.S. Pat. Nos. 3,292,335; 3,449,882; 3,694,988; 4,063,397 and 5,107,654.
The chair of this invention is a generally rectangular or box shaped structure having two walls that are generally parallel and two intersecting walls that are generally parallel. A groove is provided in at least most of the walls and preferably in all of the walls. The grooves are of different width to receive and support rebar of different diameter. The grooves are preferably in the center of each wall so the load on the chair is evenly distributed to the opposite wall. A pair of intersecting wall-like braces extend across the walls of the chair on the inside of the perimeter to reinforce the grooves and thereby strengthen the chair. The grooves run in the short direction of the chair so the braces do not block movement of concrete through the interior of the chair.
The corners of the chair are preferably angled to allow concrete to move readily into and out of the inside of the chair to promote even distribution of concrete and minimize the creation or retention of air pockets. A series of slots are provided in the walls to allow trapped air to more readily migrate upwardly out of the concrete.
It is an object of this invention to provide an improved chair to support metal reinforcements during a concrete pour.
Another object of this invention is to provide a chair having the capability of supporting a wide range of rebar and/or wire mesh during a concrete pour.
Another object of this invention is to provide a chair having the capability of supporting metal reinforcements at different elevations above an underlying surface.
A further object of this invention is to provide a chair that is sturdy and provides a wide base of support for metal reinforcements used in a concrete pour.
These and other objects of this invention will become more fully apparent as this description proceeds, reference being made to the accompanying drawings and appended claims.